/* ****************************************************************** * Huffman encoder, part of New Generation Entropy library * Copyright (c) Meta Platforms, Inc. and affiliates. * * You can contact the author at : * - FSE+HUF source repository : https://github.com/Cyan4973/FiniteStateEntropy * - Public forum : https://groups.google.com/forum/#!forum/lz4c * * This source code is licensed under both the BSD-style license (found in the * LICENSE file in the root directory of this source tree) and the GPLv2 (found * in the COPYING file in the root directory of this source tree). * You may select, at your option, one of the above-listed licenses. ****************************************************************** */ /* ************************************************************** * Compiler specifics ****************************************************************/ #ifdef _MSC_VER /* Visual Studio */ # pragma warning(disable : 4127) /* disable: C4127: conditional expression is constant */ #endif /* ************************************************************** * Includes ****************************************************************/ #include "../common/zstd_deps.h" /* ZSTD_memcpy, ZSTD_memset */ #include "../common/compiler.h" #include "../common/bitstream.h" #include "hist.h" #define FSE_STATIC_LINKING_ONLY /* FSE_optimalTableLog_internal */ #include "../common/fse.h" /* header compression */ #include "../common/huf.h" #include "../common/error_private.h" #include "../common/bits.h" /* ZSTD_highbit32 */ /* ************************************************************** * Error Management ****************************************************************/ #define HUF_isError ERR_isError #define HUF_STATIC_ASSERT(c) DEBUG_STATIC_ASSERT(c) /* use only *after* variable declarations */ /* ************************************************************** * Required declarations ****************************************************************/ typedef struct nodeElt_s { U32 count; U16 parent; BYTE byte; BYTE nbBits; } nodeElt; /* ************************************************************** * Debug Traces ****************************************************************/ #if DEBUGLEVEL >= 2 static size_t showU32(const U32* arr, size_t size) { size_t u; for (u=0; u= add) { assert(add < align); assert(((size_t)aligned & mask) == 0); *workspaceSizePtr -= add; return aligned; } else { *workspaceSizePtr = 0; return NULL; } } /* HUF_compressWeights() : * Same as FSE_compress(), but dedicated to huff0's weights compression. * The use case needs much less stack memory. * Note : all elements within weightTable are supposed to be <= HUF_TABLELOG_MAX. */ #define MAX_FSE_TABLELOG_FOR_HUFF_HEADER 6 typedef struct { FSE_CTable CTable[FSE_CTABLE_SIZE_U32(MAX_FSE_TABLELOG_FOR_HUFF_HEADER, HUF_TABLELOG_MAX)]; U32 scratchBuffer[FSE_BUILD_CTABLE_WORKSPACE_SIZE_U32(HUF_TABLELOG_MAX, MAX_FSE_TABLELOG_FOR_HUFF_HEADER)]; unsigned count[HUF_TABLELOG_MAX+1]; S16 norm[HUF_TABLELOG_MAX+1]; } HUF_CompressWeightsWksp; static size_t HUF_compressWeights(void* dst, size_t dstSize, const void* weightTable, size_t wtSize, void* workspace, size_t workspaceSize) { BYTE* const ostart = (BYTE*) dst; BYTE* op = ostart; BYTE* const oend = ostart + dstSize; unsigned maxSymbolValue = HUF_TABLELOG_MAX; U32 tableLog = MAX_FSE_TABLELOG_FOR_HUFF_HEADER; HUF_CompressWeightsWksp* wksp = (HUF_CompressWeightsWksp*)HUF_alignUpWorkspace(workspace, &workspaceSize, ZSTD_ALIGNOF(U32)); if (workspaceSize < sizeof(HUF_CompressWeightsWksp)) return ERROR(GENERIC); /* init conditions */ if (wtSize <= 1) return 0; /* Not compressible */ /* Scan input and build symbol stats */ { unsigned const maxCount = HIST_count_simple(wksp->count, &maxSymbolValue, weightTable, wtSize); /* never fails */ if (maxCount == wtSize) return 1; /* only a single symbol in src : rle */ if (maxCount == 1) return 0; /* each symbol present maximum once => not compressible */ } tableLog = FSE_optimalTableLog(tableLog, wtSize, maxSymbolValue); CHECK_F( FSE_normalizeCount(wksp->norm, tableLog, wksp->count, wtSize, maxSymbolValue, /* useLowProbCount */ 0) ); /* Write table description header */ { CHECK_V_F(hSize, FSE_writeNCount(op, (size_t)(oend-op), wksp->norm, maxSymbolValue, tableLog) ); op += hSize; } /* Compress */ CHECK_F( FSE_buildCTable_wksp(wksp->CTable, wksp->norm, maxSymbolValue, tableLog, wksp->scratchBuffer, sizeof(wksp->scratchBuffer)) ); { CHECK_V_F(cSize, FSE_compress_usingCTable(op, (size_t)(oend - op), weightTable, wtSize, wksp->CTable) ); if (cSize == 0) return 0; /* not enough space for compressed data */ op += cSize; } return (size_t)(op-ostart); } static size_t HUF_getNbBits(HUF_CElt elt) { return elt & 0xFF; } static size_t HUF_getNbBitsFast(HUF_CElt elt) { return elt; } static size_t HUF_getValue(HUF_CElt elt) { return elt & ~(size_t)0xFF; } static size_t HUF_getValueFast(HUF_CElt elt) { return elt; } static void HUF_setNbBits(HUF_CElt* elt, size_t nbBits) { assert(nbBits <= HUF_TABLELOG_ABSOLUTEMAX); *elt = nbBits; } static void HUF_setValue(HUF_CElt* elt, size_t value) { size_t const nbBits = HUF_getNbBits(*elt); if (nbBits > 0) { assert((value >> nbBits) == 0); *elt |= value << (sizeof(HUF_CElt) * 8 - nbBits); } } HUF_CTableHeader HUF_readCTableHeader(HUF_CElt const* ctable) { HUF_CTableHeader header; ZSTD_memcpy(&header, ctable, sizeof(header)); return header; } static void HUF_writeCTableHeader(HUF_CElt* ctable, U32 tableLog, U32 maxSymbolValue) { HUF_CTableHeader header; HUF_STATIC_ASSERT(sizeof(ctable[0]) == sizeof(header)); ZSTD_memset(&header, 0, sizeof(header)); assert(tableLog < 256); header.tableLog = (BYTE)tableLog; assert(maxSymbolValue < 256); header.maxSymbolValue = (BYTE)maxSymbolValue; ZSTD_memcpy(ctable, &header, sizeof(header)); } typedef struct { HUF_CompressWeightsWksp wksp; BYTE bitsToWeight[HUF_TABLELOG_MAX + 1]; /* precomputed conversion table */ BYTE huffWeight[HUF_SYMBOLVALUE_MAX]; } HUF_WriteCTableWksp; size_t HUF_writeCTable_wksp(void* dst, size_t maxDstSize, const HUF_CElt* CTable, unsigned maxSymbolValue, unsigned huffLog, void* workspace, size_t workspaceSize) { HUF_CElt const* const ct = CTable + 1; BYTE* op = (BYTE*)dst; U32 n; HUF_WriteCTableWksp* wksp = (HUF_WriteCTableWksp*)HUF_alignUpWorkspace(workspace, &workspaceSize, ZSTD_ALIGNOF(U32)); HUF_STATIC_ASSERT(HUF_CTABLE_WORKSPACE_SIZE >= sizeof(HUF_WriteCTableWksp)); assert(HUF_readCTableHeader(CTable).maxSymbolValue == maxSymbolValue); assert(HUF_readCTableHeader(CTable).tableLog == huffLog); /* check conditions */ if (workspaceSize < sizeof(HUF_WriteCTableWksp)) return ERROR(GENERIC); if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(maxSymbolValue_tooLarge); /* convert to weight */ wksp->bitsToWeight[0] = 0; for (n=1; nbitsToWeight[n] = (BYTE)(huffLog + 1 - n); for (n=0; nhuffWeight[n] = wksp->bitsToWeight[HUF_getNbBits(ct[n])]; /* attempt weights compression by FSE */ if (maxDstSize < 1) return ERROR(dstSize_tooSmall); { CHECK_V_F(hSize, HUF_compressWeights(op+1, maxDstSize-1, wksp->huffWeight, maxSymbolValue, &wksp->wksp, sizeof(wksp->wksp)) ); if ((hSize>1) & (hSize < maxSymbolValue/2)) { /* FSE compressed */ op[0] = (BYTE)hSize; return hSize+1; } } /* write raw values as 4-bits (max : 15) */ if (maxSymbolValue > (256-128)) return ERROR(GENERIC); /* should not happen : likely means source cannot be compressed */ if (((maxSymbolValue+1)/2) + 1 > maxDstSize) return ERROR(dstSize_tooSmall); /* not enough space within dst buffer */ op[0] = (BYTE)(128 /*special case*/ + (maxSymbolValue-1)); wksp->huffWeight[maxSymbolValue] = 0; /* to be sure it doesn't cause msan issue in final combination */ for (n=0; nhuffWeight[n] << 4) + wksp->huffWeight[n+1]); return ((maxSymbolValue+1)/2) + 1; } size_t HUF_readCTable (HUF_CElt* CTable, unsigned* maxSymbolValuePtr, const void* src, size_t srcSize, unsigned* hasZeroWeights) { BYTE huffWeight[HUF_SYMBOLVALUE_MAX + 1]; /* init not required, even though some static analyzer may complain */ U32 rankVal[HUF_TABLELOG_ABSOLUTEMAX + 1]; /* large enough for values from 0 to 16 */ U32 tableLog = 0; U32 nbSymbols = 0; HUF_CElt* const ct = CTable + 1; /* get symbol weights */ CHECK_V_F(readSize, HUF_readStats(huffWeight, HUF_SYMBOLVALUE_MAX+1, rankVal, &nbSymbols, &tableLog, src, srcSize)); *hasZeroWeights = (rankVal[0] > 0); /* check result */ if (tableLog > HUF_TABLELOG_MAX) return ERROR(tableLog_tooLarge); if (nbSymbols > *maxSymbolValuePtr+1) return ERROR(maxSymbolValue_tooSmall); *maxSymbolValuePtr = nbSymbols - 1; HUF_writeCTableHeader(CTable, tableLog, *maxSymbolValuePtr); /* Prepare base value per rank */ { U32 n, nextRankStart = 0; for (n=1; n<=tableLog; n++) { U32 curr = nextRankStart; nextRankStart += (rankVal[n] << (n-1)); rankVal[n] = curr; } } /* fill nbBits */ { U32 n; for (n=0; nn=tableLog+1 */ U16 valPerRank[HUF_TABLELOG_MAX+2] = {0}; { U32 n; for (n=0; n0; n--) { /* start at n=tablelog <-> w=1 */ valPerRank[n] = min; /* get starting value within each rank */ min += nbPerRank[n]; min >>= 1; } } /* assign value within rank, symbol order */ { U32 n; for (n=0; n HUF_readCTableHeader(CTable).maxSymbolValue) return 0; return (U32)HUF_getNbBits(ct[symbolValue]); } /** * HUF_setMaxHeight(): * Try to enforce @targetNbBits on the Huffman tree described in @huffNode. * * It attempts to convert all nodes with nbBits > @targetNbBits * to employ @targetNbBits instead. Then it adjusts the tree * so that it remains a valid canonical Huffman tree. * * @pre The sum of the ranks of each symbol == 2^largestBits, * where largestBits == huffNode[lastNonNull].nbBits. * @post The sum of the ranks of each symbol == 2^largestBits, * where largestBits is the return value (expected <= targetNbBits). * * @param huffNode The Huffman tree modified in place to enforce targetNbBits. * It's presumed sorted, from most frequent to rarest symbol. * @param lastNonNull The symbol with the lowest count in the Huffman tree. * @param targetNbBits The allowed number of bits, which the Huffman tree * may not respect. After this function the Huffman tree will * respect targetNbBits. * @return The maximum number of bits of the Huffman tree after adjustment. */ static U32 HUF_setMaxHeight(nodeElt* huffNode, U32 lastNonNull, U32 targetNbBits) { const U32 largestBits = huffNode[lastNonNull].nbBits; /* early exit : no elt > targetNbBits, so the tree is already valid. */ if (largestBits <= targetNbBits) return largestBits; DEBUGLOG(5, "HUF_setMaxHeight (targetNbBits = %u)", targetNbBits); /* there are several too large elements (at least >= 2) */ { int totalCost = 0; const U32 baseCost = 1 << (largestBits - targetNbBits); int n = (int)lastNonNull; /* Adjust any ranks > targetNbBits to targetNbBits. * Compute totalCost, which is how far the sum of the ranks is * we are over 2^largestBits after adjust the offending ranks. */ while (huffNode[n].nbBits > targetNbBits) { totalCost += baseCost - (1 << (largestBits - huffNode[n].nbBits)); huffNode[n].nbBits = (BYTE)targetNbBits; n--; } /* n stops at huffNode[n].nbBits <= targetNbBits */ assert(huffNode[n].nbBits <= targetNbBits); /* n end at index of smallest symbol using < targetNbBits */ while (huffNode[n].nbBits == targetNbBits) --n; /* renorm totalCost from 2^largestBits to 2^targetNbBits * note : totalCost is necessarily a multiple of baseCost */ assert(((U32)totalCost & (baseCost - 1)) == 0); totalCost >>= (largestBits - targetNbBits); assert(totalCost > 0); /* repay normalized cost */ { U32 const noSymbol = 0xF0F0F0F0; U32 rankLast[HUF_TABLELOG_MAX+2]; /* Get pos of last (smallest = lowest cum. count) symbol per rank */ ZSTD_memset(rankLast, 0xF0, sizeof(rankLast)); { U32 currentNbBits = targetNbBits; int pos; for (pos=n ; pos >= 0; pos--) { if (huffNode[pos].nbBits >= currentNbBits) continue; currentNbBits = huffNode[pos].nbBits; /* < targetNbBits */ rankLast[targetNbBits-currentNbBits] = (U32)pos; } } while (totalCost > 0) { /* Try to reduce the next power of 2 above totalCost because we * gain back half the rank. */ U32 nBitsToDecrease = ZSTD_highbit32((U32)totalCost) + 1; for ( ; nBitsToDecrease > 1; nBitsToDecrease--) { U32 const highPos = rankLast[nBitsToDecrease]; U32 const lowPos = rankLast[nBitsToDecrease-1]; if (highPos == noSymbol) continue; /* Decrease highPos if no symbols of lowPos or if it is * not cheaper to remove 2 lowPos than highPos. */ if (lowPos == noSymbol) break; { U32 const highTotal = huffNode[highPos].count; U32 const lowTotal = 2 * huffNode[lowPos].count; if (highTotal <= lowTotal) break; } } /* only triggered when no more rank 1 symbol left => find closest one (note : there is necessarily at least one !) */ assert(rankLast[nBitsToDecrease] != noSymbol || nBitsToDecrease == 1); /* HUF_MAX_TABLELOG test just to please gcc 5+; but it should not be necessary */ while ((nBitsToDecrease<=HUF_TABLELOG_MAX) && (rankLast[nBitsToDecrease] == noSymbol)) nBitsToDecrease++; assert(rankLast[nBitsToDecrease] != noSymbol); /* Increase the number of bits to gain back half the rank cost. */ totalCost -= 1 << (nBitsToDecrease-1); huffNode[rankLast[nBitsToDecrease]].nbBits++; /* Fix up the new rank. * If the new rank was empty, this symbol is now its smallest. * Otherwise, this symbol will be the largest in the new rank so no adjustment. */ if (rankLast[nBitsToDecrease-1] == noSymbol) rankLast[nBitsToDecrease-1] = rankLast[nBitsToDecrease]; /* Fix up the old rank. * If the symbol was at position 0, meaning it was the highest weight symbol in the tree, * it must be the only symbol in its rank, so the old rank now has no symbols. * Otherwise, since the Huffman nodes are sorted by count, the previous position is now * the smallest node in the rank. If the previous position belongs to a different rank, * then the rank is now empty. */ if (rankLast[nBitsToDecrease] == 0) /* special case, reached largest symbol */ rankLast[nBitsToDecrease] = noSymbol; else { rankLast[nBitsToDecrease]--; if (huffNode[rankLast[nBitsToDecrease]].nbBits != targetNbBits-nBitsToDecrease) rankLast[nBitsToDecrease] = noSymbol; /* this rank is now empty */ } } /* while (totalCost > 0) */ /* If we've removed too much weight, then we have to add it back. * To avoid overshooting again, we only adjust the smallest rank. * We take the largest nodes from the lowest rank 0 and move them * to rank 1. There's guaranteed to be enough rank 0 symbols because * TODO. */ while (totalCost < 0) { /* Sometimes, cost correction overshoot */ /* special case : no rank 1 symbol (using targetNbBits-1); * let's create one from largest rank 0 (using targetNbBits). */ if (rankLast[1] == noSymbol) { while (huffNode[n].nbBits == targetNbBits) n--; huffNode[n+1].nbBits--; assert(n >= 0); rankLast[1] = (U32)(n+1); totalCost++; continue; } huffNode[ rankLast[1] + 1 ].nbBits--; rankLast[1]++; totalCost ++; } } /* repay normalized cost */ } /* there are several too large elements (at least >= 2) */ return targetNbBits; } typedef struct { U16 base; U16 curr; } rankPos; typedef nodeElt huffNodeTable[2 * (HUF_SYMBOLVALUE_MAX + 1)]; /* Number of buckets available for HUF_sort() */ #define RANK_POSITION_TABLE_SIZE 192 typedef struct { huffNodeTable huffNodeTbl; rankPos rankPosition[RANK_POSITION_TABLE_SIZE]; } HUF_buildCTable_wksp_tables; /* RANK_POSITION_DISTINCT_COUNT_CUTOFF == Cutoff point in HUF_sort() buckets for which we use log2 bucketing. * Strategy is to use as many buckets as possible for representing distinct * counts while using the remainder to represent all "large" counts. * * To satisfy this requirement for 192 buckets, we can do the following: * Let buckets 0-166 represent distinct counts of [0, 166] * Let buckets 166 to 192 represent all remaining counts up to RANK_POSITION_MAX_COUNT_LOG using log2 bucketing. */ #define RANK_POSITION_MAX_COUNT_LOG 32 #define RANK_POSITION_LOG_BUCKETS_BEGIN ((RANK_POSITION_TABLE_SIZE - 1) - RANK_POSITION_MAX_COUNT_LOG - 1 /* == 158 */) #define RANK_POSITION_DISTINCT_COUNT_CUTOFF (RANK_POSITION_LOG_BUCKETS_BEGIN + ZSTD_highbit32(RANK_POSITION_LOG_BUCKETS_BEGIN) /* == 166 */) /* Return the appropriate bucket index for a given count. See definition of * RANK_POSITION_DISTINCT_COUNT_CUTOFF for explanation of bucketing strategy. */ static U32 HUF_getIndex(U32 const count) { return (count < RANK_POSITION_DISTINCT_COUNT_CUTOFF) ? count : ZSTD_highbit32(count) + RANK_POSITION_LOG_BUCKETS_BEGIN; } /* Helper swap function for HUF_quickSortPartition() */ static void HUF_swapNodes(nodeElt* a, nodeElt* b) { nodeElt tmp = *a; *a = *b; *b = tmp; } /* Returns 0 if the huffNode array is not sorted by descending count */ MEM_STATIC int HUF_isSorted(nodeElt huffNode[], U32 const maxSymbolValue1) { U32 i; for (i = 1; i < maxSymbolValue1; ++i) { if (huffNode[i].count > huffNode[i-1].count) { return 0; } } return 1; } /* Insertion sort by descending order */ HINT_INLINE void HUF_insertionSort(nodeElt huffNode[], int const low, int const high) { int i; int const size = high-low+1; huffNode += low; for (i = 1; i < size; ++i) { nodeElt const key = huffNode[i]; int j = i - 1; while (j >= 0 && huffNode[j].count < key.count) { huffNode[j + 1] = huffNode[j]; j--; } huffNode[j + 1] = key; } } /* Pivot helper function for quicksort. */ static int HUF_quickSortPartition(nodeElt arr[], int const low, int const high) { /* Simply select rightmost element as pivot. "Better" selectors like * median-of-three don't experimentally appear to have any benefit. */ U32 const pivot = arr[high].count; int i = low - 1; int j = low; for ( ; j < high; j++) { if (arr[j].count > pivot) { i++; HUF_swapNodes(&arr[i], &arr[j]); } } HUF_swapNodes(&arr[i + 1], &arr[high]); return i + 1; } /* Classic quicksort by descending with partially iterative calls * to reduce worst case callstack size. */ static void HUF_simpleQuickSort(nodeElt arr[], int low, int high) { int const kInsertionSortThreshold = 8; if (high - low < kInsertionSortThreshold) { HUF_insertionSort(arr, low, high); return; } while (low < high) { int const idx = HUF_quickSortPartition(arr, low, high); if (idx - low < high - idx) { HUF_simpleQuickSort(arr, low, idx - 1); low = idx + 1; } else { HUF_simpleQuickSort(arr, idx + 1, high); high = idx - 1; } } } /** * HUF_sort(): * Sorts the symbols [0, maxSymbolValue] by count[symbol] in decreasing order. * This is a typical bucket sorting strategy that uses either quicksort or insertion sort to sort each bucket. * * @param[out] huffNode Sorted symbols by decreasing count. Only members `.count` and `.byte` are filled. * Must have (maxSymbolValue + 1) entries. * @param[in] count Histogram of the symbols. * @param[in] maxSymbolValue Maximum symbol value. * @param rankPosition This is a scratch workspace. Must have RANK_POSITION_TABLE_SIZE entries. */ static void HUF_sort(nodeElt huffNode[], const unsigned count[], U32 const maxSymbolValue, rankPos rankPosition[]) { U32 n; U32 const maxSymbolValue1 = maxSymbolValue+1; /* Compute base and set curr to base. * For symbol s let lowerRank = HUF_getIndex(count[n]) and rank = lowerRank + 1. * See HUF_getIndex to see bucketing strategy. * We attribute each symbol to lowerRank's base value, because we want to know where * each rank begins in the output, so for rank R we want to count ranks R+1 and above. */ ZSTD_memset(rankPosition, 0, sizeof(*rankPosition) * RANK_POSITION_TABLE_SIZE); for (n = 0; n < maxSymbolValue1; ++n) { U32 lowerRank = HUF_getIndex(count[n]); assert(lowerRank < RANK_POSITION_TABLE_SIZE - 1); rankPosition[lowerRank].base++; } assert(rankPosition[RANK_POSITION_TABLE_SIZE - 1].base == 0); /* Set up the rankPosition table */ for (n = RANK_POSITION_TABLE_SIZE - 1; n > 0; --n) { rankPosition[n-1].base += rankPosition[n].base; rankPosition[n-1].curr = rankPosition[n-1].base; } /* Insert each symbol into their appropriate bucket, setting up rankPosition table. */ for (n = 0; n < maxSymbolValue1; ++n) { U32 const c = count[n]; U32 const r = HUF_getIndex(c) + 1; U32 const pos = rankPosition[r].curr++; assert(pos < maxSymbolValue1); huffNode[pos].count = c; huffNode[pos].byte = (BYTE)n; } /* Sort each bucket. */ for (n = RANK_POSITION_DISTINCT_COUNT_CUTOFF; n < RANK_POSITION_TABLE_SIZE - 1; ++n) { int const bucketSize = rankPosition[n].curr - rankPosition[n].base; U32 const bucketStartIdx = rankPosition[n].base; if (bucketSize > 1) { assert(bucketStartIdx < maxSymbolValue1); HUF_simpleQuickSort(huffNode + bucketStartIdx, 0, bucketSize-1); } } assert(HUF_isSorted(huffNode, maxSymbolValue1)); } /** HUF_buildCTable_wksp() : * Same as HUF_buildCTable(), but using externally allocated scratch buffer. * `workSpace` must be aligned on 4-bytes boundaries, and be at least as large as sizeof(HUF_buildCTable_wksp_tables). */ #define STARTNODE (HUF_SYMBOLVALUE_MAX+1) /* HUF_buildTree(): * Takes the huffNode array sorted by HUF_sort() and builds an unlimited-depth Huffman tree. * * @param huffNode The array sorted by HUF_sort(). Builds the Huffman tree in this array. * @param maxSymbolValue The maximum symbol value. * @return The smallest node in the Huffman tree (by count). */ static int HUF_buildTree(nodeElt* huffNode, U32 maxSymbolValue) { nodeElt* const huffNode0 = huffNode - 1; int nonNullRank; int lowS, lowN; int nodeNb = STARTNODE; int n, nodeRoot; DEBUGLOG(5, "HUF_buildTree (alphabet size = %u)", maxSymbolValue + 1); /* init for parents */ nonNullRank = (int)maxSymbolValue; while(huffNode[nonNullRank].count == 0) nonNullRank--; lowS = nonNullRank; nodeRoot = nodeNb + lowS - 1; lowN = nodeNb; huffNode[nodeNb].count = huffNode[lowS].count + huffNode[lowS-1].count; huffNode[lowS].parent = huffNode[lowS-1].parent = (U16)nodeNb; nodeNb++; lowS-=2; for (n=nodeNb; n<=nodeRoot; n++) huffNode[n].count = (U32)(1U<<30); huffNode0[0].count = (U32)(1U<<31); /* fake entry, strong barrier */ /* create parents */ while (nodeNb <= nodeRoot) { int const n1 = (huffNode[lowS].count < huffNode[lowN].count) ? lowS-- : lowN++; int const n2 = (huffNode[lowS].count < huffNode[lowN].count) ? lowS-- : lowN++; huffNode[nodeNb].count = huffNode[n1].count + huffNode[n2].count; huffNode[n1].parent = huffNode[n2].parent = (U16)nodeNb; nodeNb++; } /* distribute weights (unlimited tree height) */ huffNode[nodeRoot].nbBits = 0; for (n=nodeRoot-1; n>=STARTNODE; n--) huffNode[n].nbBits = huffNode[ huffNode[n].parent ].nbBits + 1; for (n=0; n<=nonNullRank; n++) huffNode[n].nbBits = huffNode[ huffNode[n].parent ].nbBits + 1; DEBUGLOG(6, "Initial distribution of bits completed (%zu sorted symbols)", showHNodeBits(huffNode, maxSymbolValue+1)); return nonNullRank; } /** * HUF_buildCTableFromTree(): * Build the CTable given the Huffman tree in huffNode. * * @param[out] CTable The output Huffman CTable. * @param huffNode The Huffman tree. * @param nonNullRank The last and smallest node in the Huffman tree. * @param maxSymbolValue The maximum symbol value. * @param maxNbBits The exact maximum number of bits used in the Huffman tree. */ static void HUF_buildCTableFromTree(HUF_CElt* CTable, nodeElt const* huffNode, int nonNullRank, U32 maxSymbolValue, U32 maxNbBits) { HUF_CElt* const ct = CTable + 1; /* fill result into ctable (val, nbBits) */ int n; U16 nbPerRank[HUF_TABLELOG_MAX+1] = {0}; U16 valPerRank[HUF_TABLELOG_MAX+1] = {0}; int const alphabetSize = (int)(maxSymbolValue + 1); for (n=0; n<=nonNullRank; n++) nbPerRank[huffNode[n].nbBits]++; /* determine starting value per rank */ { U16 min = 0; for (n=(int)maxNbBits; n>0; n--) { valPerRank[n] = min; /* get starting value within each rank */ min += nbPerRank[n]; min >>= 1; } } for (n=0; nhuffNodeTbl; nodeElt* const huffNode = huffNode0+1; int nonNullRank; HUF_STATIC_ASSERT(HUF_CTABLE_WORKSPACE_SIZE == sizeof(HUF_buildCTable_wksp_tables)); DEBUGLOG(5, "HUF_buildCTable_wksp (alphabet size = %u)", maxSymbolValue+1); /* safety checks */ if (wkspSize < sizeof(HUF_buildCTable_wksp_tables)) return ERROR(workSpace_tooSmall); if (maxNbBits == 0) maxNbBits = HUF_TABLELOG_DEFAULT; if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(maxSymbolValue_tooLarge); ZSTD_memset(huffNode0, 0, sizeof(huffNodeTable)); /* sort, decreasing order */ HUF_sort(huffNode, count, maxSymbolValue, wksp_tables->rankPosition); DEBUGLOG(6, "sorted symbols completed (%zu symbols)", showHNodeSymbols(huffNode, maxSymbolValue+1)); /* build tree */ nonNullRank = HUF_buildTree(huffNode, maxSymbolValue); /* determine and enforce maxTableLog */ maxNbBits = HUF_setMaxHeight(huffNode, (U32)nonNullRank, maxNbBits); if (maxNbBits > HUF_TABLELOG_MAX) return ERROR(GENERIC); /* check fit into table */ HUF_buildCTableFromTree(CTable, huffNode, nonNullRank, maxSymbolValue, maxNbBits); return maxNbBits; } size_t HUF_estimateCompressedSize(const HUF_CElt* CTable, const unsigned* count, unsigned maxSymbolValue) { HUF_CElt const* ct = CTable + 1; size_t nbBits = 0; int s; for (s = 0; s <= (int)maxSymbolValue; ++s) { nbBits += HUF_getNbBits(ct[s]) * count[s]; } return nbBits >> 3; } int HUF_validateCTable(const HUF_CElt* CTable, const unsigned* count, unsigned maxSymbolValue) { HUF_CTableHeader header = HUF_readCTableHeader(CTable); HUF_CElt const* ct = CTable + 1; int bad = 0; int s; assert(header.tableLog <= HUF_TABLELOG_ABSOLUTEMAX); if (header.maxSymbolValue < maxSymbolValue) return 0; for (s = 0; s <= (int)maxSymbolValue; ++s) { bad |= (count[s] != 0) & (HUF_getNbBits(ct[s]) == 0); } return !bad; } size_t HUF_compressBound(size_t size) { return HUF_COMPRESSBOUND(size); } /** HUF_CStream_t: * Huffman uses its own BIT_CStream_t implementation. * There are three major differences from BIT_CStream_t: * 1. HUF_addBits() takes a HUF_CElt (size_t) which is * the pair (nbBits, value) in the format: * format: * - Bits [0, 4) = nbBits * - Bits [4, 64 - nbBits) = 0 * - Bits [64 - nbBits, 64) = value * 2. The bitContainer is built from the upper bits and * right shifted. E.g. to add a new value of N bits * you right shift the bitContainer by N, then or in * the new value into the N upper bits. * 3. The bitstream has two bit containers. You can add * bits to the second container and merge them into * the first container. */ #define HUF_BITS_IN_CONTAINER (sizeof(size_t) * 8) typedef struct { size_t bitContainer[2]; size_t bitPos[2]; BYTE* startPtr; BYTE* ptr; BYTE* endPtr; } HUF_CStream_t; /**! HUF_initCStream(): * Initializes the bitstream. * @returns 0 or an error code. */ static size_t HUF_initCStream(HUF_CStream_t* bitC, void* startPtr, size_t dstCapacity) { ZSTD_memset(bitC, 0, sizeof(*bitC)); bitC->startPtr = (BYTE*)startPtr; bitC->ptr = bitC->startPtr; bitC->endPtr = bitC->startPtr + dstCapacity - sizeof(bitC->bitContainer[0]); if (dstCapacity <= sizeof(bitC->bitContainer[0])) return ERROR(dstSize_tooSmall); return 0; } /*! HUF_addBits(): * Adds the symbol stored in HUF_CElt elt to the bitstream. * * @param elt The element we're adding. This is a (nbBits, value) pair. * See the HUF_CStream_t docs for the format. * @param idx Insert into the bitstream at this idx. * @param kFast This is a template parameter. If the bitstream is guaranteed * to have at least 4 unused bits after this call it may be 1, * otherwise it must be 0. HUF_addBits() is faster when fast is set. */ FORCE_INLINE_TEMPLATE void HUF_addBits(HUF_CStream_t* bitC, HUF_CElt elt, int idx, int kFast) { assert(idx <= 1); assert(HUF_getNbBits(elt) <= HUF_TABLELOG_ABSOLUTEMAX); /* This is efficient on x86-64 with BMI2 because shrx * only reads the low 6 bits of the register. The compiler * knows this and elides the mask. When fast is set, * every operation can use the same value loaded from elt. */ bitC->bitContainer[idx] >>= HUF_getNbBits(elt); bitC->bitContainer[idx] |= kFast ? HUF_getValueFast(elt) : HUF_getValue(elt); /* We only read the low 8 bits of bitC->bitPos[idx] so it * doesn't matter that the high bits have noise from the value. */ bitC->bitPos[idx] += HUF_getNbBitsFast(elt); assert((bitC->bitPos[idx] & 0xFF) <= HUF_BITS_IN_CONTAINER); /* The last 4-bits of elt are dirty if fast is set, * so we must not be overwriting bits that have already been * inserted into the bit container. */ #if DEBUGLEVEL >= 1 { size_t const nbBits = HUF_getNbBits(elt); size_t const dirtyBits = nbBits == 0 ? 0 : ZSTD_highbit32((U32)nbBits) + 1; (void)dirtyBits; /* Middle bits are 0. */ assert(((elt >> dirtyBits) << (dirtyBits + nbBits)) == 0); /* We didn't overwrite any bits in the bit container. */ assert(!kFast || (bitC->bitPos[idx] & 0xFF) <= HUF_BITS_IN_CONTAINER); (void)dirtyBits; } #endif } FORCE_INLINE_TEMPLATE void HUF_zeroIndex1(HUF_CStream_t* bitC) { bitC->bitContainer[1] = 0; bitC->bitPos[1] = 0; } /*! HUF_mergeIndex1() : * Merges the bit container @ index 1 into the bit container @ index 0 * and zeros the bit container @ index 1. */ FORCE_INLINE_TEMPLATE void HUF_mergeIndex1(HUF_CStream_t* bitC) { assert((bitC->bitPos[1] & 0xFF) < HUF_BITS_IN_CONTAINER); bitC->bitContainer[0] >>= (bitC->bitPos[1] & 0xFF); bitC->bitContainer[0] |= bitC->bitContainer[1]; bitC->bitPos[0] += bitC->bitPos[1]; assert((bitC->bitPos[0] & 0xFF) <= HUF_BITS_IN_CONTAINER); } /*! HUF_flushBits() : * Flushes the bits in the bit container @ index 0. * * @post bitPos will be < 8. * @param kFast If kFast is set then we must know a-priori that * the bit container will not overflow. */ FORCE_INLINE_TEMPLATE void HUF_flushBits(HUF_CStream_t* bitC, int kFast) { /* The upper bits of bitPos are noisy, so we must mask by 0xFF. */ size_t const nbBits = bitC->bitPos[0] & 0xFF; size_t const nbBytes = nbBits >> 3; /* The top nbBits bits of bitContainer are the ones we need. */ size_t const bitContainer = bitC->bitContainer[0] >> (HUF_BITS_IN_CONTAINER - nbBits); /* Mask bitPos to account for the bytes we consumed. */ bitC->bitPos[0] &= 7; assert(nbBits > 0); assert(nbBits <= sizeof(bitC->bitContainer[0]) * 8); assert(bitC->ptr <= bitC->endPtr); MEM_writeLEST(bitC->ptr, bitContainer); bitC->ptr += nbBytes; assert(!kFast || bitC->ptr <= bitC->endPtr); if (!kFast && bitC->ptr > bitC->endPtr) bitC->ptr = bitC->endPtr; /* bitContainer doesn't need to be modified because the leftover * bits are already the top bitPos bits. And we don't care about * noise in the lower values. */ } /*! HUF_endMark() * @returns The Huffman stream end mark: A 1-bit value = 1. */ static HUF_CElt HUF_endMark(void) { HUF_CElt endMark; HUF_setNbBits(&endMark, 1); HUF_setValue(&endMark, 1); return endMark; } /*! HUF_closeCStream() : * @return Size of CStream, in bytes, * or 0 if it could not fit into dstBuffer */ static size_t HUF_closeCStream(HUF_CStream_t* bitC) { HUF_addBits(bitC, HUF_endMark(), /* idx */ 0, /* kFast */ 0); HUF_flushBits(bitC, /* kFast */ 0); { size_t const nbBits = bitC->bitPos[0] & 0xFF; if (bitC->ptr >= bitC->endPtr) return 0; /* overflow detected */ return (size_t)(bitC->ptr - bitC->startPtr) + (nbBits > 0); } } FORCE_INLINE_TEMPLATE void HUF_encodeSymbol(HUF_CStream_t* bitCPtr, U32 symbol, const HUF_CElt* CTable, int idx, int fast) { HUF_addBits(bitCPtr, CTable[symbol], idx, fast); } FORCE_INLINE_TEMPLATE void HUF_compress1X_usingCTable_internal_body_loop(HUF_CStream_t* bitC, const BYTE* ip, size_t srcSize, const HUF_CElt* ct, int kUnroll, int kFastFlush, int kLastFast) { /* Join to kUnroll */ int n = (int)srcSize; int rem = n % kUnroll; if (rem > 0) { for (; rem > 0; --rem) { HUF_encodeSymbol(bitC, ip[--n], ct, 0, /* fast */ 0); } HUF_flushBits(bitC, kFastFlush); } assert(n % kUnroll == 0); /* Join to 2 * kUnroll */ if (n % (2 * kUnroll)) { int u; for (u = 1; u < kUnroll; ++u) { HUF_encodeSymbol(bitC, ip[n - u], ct, 0, 1); } HUF_encodeSymbol(bitC, ip[n - kUnroll], ct, 0, kLastFast); HUF_flushBits(bitC, kFastFlush); n -= kUnroll; } assert(n % (2 * kUnroll) == 0); for (; n>0; n-= 2 * kUnroll) { /* Encode kUnroll symbols into the bitstream @ index 0. */ int u; for (u = 1; u < kUnroll; ++u) { HUF_encodeSymbol(bitC, ip[n - u], ct, /* idx */ 0, /* fast */ 1); } HUF_encodeSymbol(bitC, ip[n - kUnroll], ct, /* idx */ 0, /* fast */ kLastFast); HUF_flushBits(bitC, kFastFlush); /* Encode kUnroll symbols into the bitstream @ index 1. * This allows us to start filling the bit container * without any data dependencies. */ HUF_zeroIndex1(bitC); for (u = 1; u < kUnroll; ++u) { HUF_encodeSymbol(bitC, ip[n - kUnroll - u], ct, /* idx */ 1, /* fast */ 1); } HUF_encodeSymbol(bitC, ip[n - kUnroll - kUnroll], ct, /* idx */ 1, /* fast */ kLastFast); /* Merge bitstream @ index 1 into the bitstream @ index 0 */ HUF_mergeIndex1(bitC); HUF_flushBits(bitC, kFastFlush); } assert(n == 0); } /** * Returns a tight upper bound on the output space needed by Huffman * with 8 bytes buffer to handle over-writes. If the output is at least * this large we don't need to do bounds checks during Huffman encoding. */ static size_t HUF_tightCompressBound(size_t srcSize, size_t tableLog) { return ((srcSize * tableLog) >> 3) + 8; } FORCE_INLINE_TEMPLATE size_t HUF_compress1X_usingCTable_internal_body(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable) { U32 const tableLog = HUF_readCTableHeader(CTable).tableLog; HUF_CElt const* ct = CTable + 1; const BYTE* ip = (const BYTE*) src; BYTE* const ostart = (BYTE*)dst; BYTE* const oend = ostart + dstSize; HUF_CStream_t bitC; /* init */ if (dstSize < 8) return 0; /* not enough space to compress */ { BYTE* op = ostart; size_t const initErr = HUF_initCStream(&bitC, op, (size_t)(oend-op)); if (HUF_isError(initErr)) return 0; } if (dstSize < HUF_tightCompressBound(srcSize, (size_t)tableLog) || tableLog > 11) HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ MEM_32bits() ? 2 : 4, /* kFast */ 0, /* kLastFast */ 0); else { if (MEM_32bits()) { switch (tableLog) { case 11: HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 2, /* kFastFlush */ 1, /* kLastFast */ 0); break; case 10: ZSTD_FALLTHROUGH; case 9: ZSTD_FALLTHROUGH; case 8: HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 2, /* kFastFlush */ 1, /* kLastFast */ 1); break; case 7: ZSTD_FALLTHROUGH; default: HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 3, /* kFastFlush */ 1, /* kLastFast */ 1); break; } } else { switch (tableLog) { case 11: HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 5, /* kFastFlush */ 1, /* kLastFast */ 0); break; case 10: HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 5, /* kFastFlush */ 1, /* kLastFast */ 1); break; case 9: HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 6, /* kFastFlush */ 1, /* kLastFast */ 0); break; case 8: HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 7, /* kFastFlush */ 1, /* kLastFast */ 0); break; case 7: HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 8, /* kFastFlush */ 1, /* kLastFast */ 0); break; case 6: ZSTD_FALLTHROUGH; default: HUF_compress1X_usingCTable_internal_body_loop(&bitC, ip, srcSize, ct, /* kUnroll */ 9, /* kFastFlush */ 1, /* kLastFast */ 1); break; } } } assert(bitC.ptr <= bitC.endPtr); return HUF_closeCStream(&bitC); } #if DYNAMIC_BMI2 static BMI2_TARGET_ATTRIBUTE size_t HUF_compress1X_usingCTable_internal_bmi2(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable) { return HUF_compress1X_usingCTable_internal_body(dst, dstSize, src, srcSize, CTable); } static size_t HUF_compress1X_usingCTable_internal_default(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable) { return HUF_compress1X_usingCTable_internal_body(dst, dstSize, src, srcSize, CTable); } static size_t HUF_compress1X_usingCTable_internal(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable, const int flags) { if (flags & HUF_flags_bmi2) { return HUF_compress1X_usingCTable_internal_bmi2(dst, dstSize, src, srcSize, CTable); } return HUF_compress1X_usingCTable_internal_default(dst, dstSize, src, srcSize, CTable); } #else static size_t HUF_compress1X_usingCTable_internal(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable, const int flags) { (void)flags; return HUF_compress1X_usingCTable_internal_body(dst, dstSize, src, srcSize, CTable); } #endif size_t HUF_compress1X_usingCTable(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable, int flags) { return HUF_compress1X_usingCTable_internal(dst, dstSize, src, srcSize, CTable, flags); } static size_t HUF_compress4X_usingCTable_internal(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable, int flags) { size_t const segmentSize = (srcSize+3)/4; /* first 3 segments */ const BYTE* ip = (const BYTE*) src; const BYTE* const iend = ip + srcSize; BYTE* const ostart = (BYTE*) dst; BYTE* const oend = ostart + dstSize; BYTE* op = ostart; if (dstSize < 6 + 1 + 1 + 1 + 8) return 0; /* minimum space to compress successfully */ if (srcSize < 12) return 0; /* no saving possible : too small input */ op += 6; /* jumpTable */ assert(op <= oend); { CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, segmentSize, CTable, flags) ); if (cSize == 0 || cSize > 65535) return 0; MEM_writeLE16(ostart, (U16)cSize); op += cSize; } ip += segmentSize; assert(op <= oend); { CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, segmentSize, CTable, flags) ); if (cSize == 0 || cSize > 65535) return 0; MEM_writeLE16(ostart+2, (U16)cSize); op += cSize; } ip += segmentSize; assert(op <= oend); { CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, segmentSize, CTable, flags) ); if (cSize == 0 || cSize > 65535) return 0; MEM_writeLE16(ostart+4, (U16)cSize); op += cSize; } ip += segmentSize; assert(op <= oend); assert(ip <= iend); { CHECK_V_F(cSize, HUF_compress1X_usingCTable_internal(op, (size_t)(oend-op), ip, (size_t)(iend-ip), CTable, flags) ); if (cSize == 0 || cSize > 65535) return 0; op += cSize; } return (size_t)(op-ostart); } size_t HUF_compress4X_usingCTable(void* dst, size_t dstSize, const void* src, size_t srcSize, const HUF_CElt* CTable, int flags) { return HUF_compress4X_usingCTable_internal(dst, dstSize, src, srcSize, CTable, flags); } typedef enum { HUF_singleStream, HUF_fourStreams } HUF_nbStreams_e; static size_t HUF_compressCTable_internal( BYTE* const ostart, BYTE* op, BYTE* const oend, const void* src, size_t srcSize, HUF_nbStreams_e nbStreams, const HUF_CElt* CTable, const int flags) { size_t const cSize = (nbStreams==HUF_singleStream) ? HUF_compress1X_usingCTable_internal(op, (size_t)(oend - op), src, srcSize, CTable, flags) : HUF_compress4X_usingCTable_internal(op, (size_t)(oend - op), src, srcSize, CTable, flags); if (HUF_isError(cSize)) { return cSize; } if (cSize==0) { return 0; } /* uncompressible */ op += cSize; /* check compressibility */ assert(op >= ostart); if ((size_t)(op-ostart) >= srcSize-1) { return 0; } return (size_t)(op-ostart); } typedef struct { unsigned count[HUF_SYMBOLVALUE_MAX + 1]; HUF_CElt CTable[HUF_CTABLE_SIZE_ST(HUF_SYMBOLVALUE_MAX)]; union { HUF_buildCTable_wksp_tables buildCTable_wksp; HUF_WriteCTableWksp writeCTable_wksp; U32 hist_wksp[HIST_WKSP_SIZE_U32]; } wksps; } HUF_compress_tables_t; #define SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE 4096 #define SUSPECT_INCOMPRESSIBLE_SAMPLE_RATIO 10 /* Must be >= 2 */ unsigned HUF_cardinality(const unsigned* count, unsigned maxSymbolValue) { unsigned cardinality = 0; unsigned i; for (i = 0; i < maxSymbolValue + 1; i++) { if (count[i] != 0) cardinality += 1; } return cardinality; } unsigned HUF_minTableLog(unsigned symbolCardinality) { U32 minBitsSymbols = ZSTD_highbit32(symbolCardinality) + 1; return minBitsSymbols; } unsigned HUF_optimalTableLog( unsigned maxTableLog, size_t srcSize, unsigned maxSymbolValue, void* workSpace, size_t wkspSize, HUF_CElt* table, const unsigned* count, int flags) { assert(srcSize > 1); /* Not supported, RLE should be used instead */ assert(wkspSize >= sizeof(HUF_buildCTable_wksp_tables)); if (!(flags & HUF_flags_optimalDepth)) { /* cheap evaluation, based on FSE */ return FSE_optimalTableLog_internal(maxTableLog, srcSize, maxSymbolValue, 1); } { BYTE* dst = (BYTE*)workSpace + sizeof(HUF_WriteCTableWksp); size_t dstSize = wkspSize - sizeof(HUF_WriteCTableWksp); size_t hSize, newSize; const unsigned symbolCardinality = HUF_cardinality(count, maxSymbolValue); const unsigned minTableLog = HUF_minTableLog(symbolCardinality); size_t optSize = ((size_t) ~0) - 1; unsigned optLog = maxTableLog, optLogGuess; DEBUGLOG(6, "HUF_optimalTableLog: probing huf depth (srcSize=%zu)", srcSize); /* Search until size increases */ for (optLogGuess = minTableLog; optLogGuess <= maxTableLog; optLogGuess++) { DEBUGLOG(7, "checking for huffLog=%u", optLogGuess); { size_t maxBits = HUF_buildCTable_wksp(table, count, maxSymbolValue, optLogGuess, workSpace, wkspSize); if (ERR_isError(maxBits)) continue; if (maxBits < optLogGuess && optLogGuess > minTableLog) break; hSize = HUF_writeCTable_wksp(dst, dstSize, table, maxSymbolValue, (U32)maxBits, workSpace, wkspSize); } if (ERR_isError(hSize)) continue; newSize = HUF_estimateCompressedSize(table, count, maxSymbolValue) + hSize; if (newSize > optSize + 1) { break; } if (newSize < optSize) { optSize = newSize; optLog = optLogGuess; } } assert(optLog <= HUF_TABLELOG_MAX); return optLog; } } /* HUF_compress_internal() : * `workSpace_align4` must be aligned on 4-bytes boundaries, * and occupies the same space as a table of HUF_WORKSPACE_SIZE_U64 unsigned */ static size_t HUF_compress_internal (void* dst, size_t dstSize, const void* src, size_t srcSize, unsigned maxSymbolValue, unsigned huffLog, HUF_nbStreams_e nbStreams, void* workSpace, size_t wkspSize, HUF_CElt* oldHufTable, HUF_repeat* repeat, int flags) { HUF_compress_tables_t* const table = (HUF_compress_tables_t*)HUF_alignUpWorkspace(workSpace, &wkspSize, ZSTD_ALIGNOF(size_t)); BYTE* const ostart = (BYTE*)dst; BYTE* const oend = ostart + dstSize; BYTE* op = ostart; DEBUGLOG(5, "HUF_compress_internal (srcSize=%zu)", srcSize); HUF_STATIC_ASSERT(sizeof(*table) + HUF_WORKSPACE_MAX_ALIGNMENT <= HUF_WORKSPACE_SIZE); /* checks & inits */ if (wkspSize < sizeof(*table)) return ERROR(workSpace_tooSmall); if (!srcSize) return 0; /* Uncompressed */ if (!dstSize) return 0; /* cannot fit anything within dst budget */ if (srcSize > HUF_BLOCKSIZE_MAX) return ERROR(srcSize_wrong); /* current block size limit */ if (huffLog > HUF_TABLELOG_MAX) return ERROR(tableLog_tooLarge); if (maxSymbolValue > HUF_SYMBOLVALUE_MAX) return ERROR(maxSymbolValue_tooLarge); if (!maxSymbolValue) maxSymbolValue = HUF_SYMBOLVALUE_MAX; if (!huffLog) huffLog = HUF_TABLELOG_DEFAULT; /* Heuristic : If old table is valid, use it for small inputs */ if ((flags & HUF_flags_preferRepeat) && repeat && *repeat == HUF_repeat_valid) { return HUF_compressCTable_internal(ostart, op, oend, src, srcSize, nbStreams, oldHufTable, flags); } /* If uncompressible data is suspected, do a smaller sampling first */ DEBUG_STATIC_ASSERT(SUSPECT_INCOMPRESSIBLE_SAMPLE_RATIO >= 2); if ((flags & HUF_flags_suspectUncompressible) && srcSize >= (SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE * SUSPECT_INCOMPRESSIBLE_SAMPLE_RATIO)) { size_t largestTotal = 0; DEBUGLOG(5, "input suspected incompressible : sampling to check"); { unsigned maxSymbolValueBegin = maxSymbolValue; CHECK_V_F(largestBegin, HIST_count_simple (table->count, &maxSymbolValueBegin, (const BYTE*)src, SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE) ); largestTotal += largestBegin; } { unsigned maxSymbolValueEnd = maxSymbolValue; CHECK_V_F(largestEnd, HIST_count_simple (table->count, &maxSymbolValueEnd, (const BYTE*)src + srcSize - SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE, SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE) ); largestTotal += largestEnd; } if (largestTotal <= ((2 * SUSPECT_INCOMPRESSIBLE_SAMPLE_SIZE) >> 7)+4) return 0; /* heuristic : probably not compressible enough */ } /* Scan input and build symbol stats */ { CHECK_V_F(largest, HIST_count_wksp (table->count, &maxSymbolValue, (const BYTE*)src, srcSize, table->wksps.hist_wksp, sizeof(table->wksps.hist_wksp)) ); if (largest == srcSize) { *ostart = ((const BYTE*)src)[0]; return 1; } /* single symbol, rle */ if (largest <= (srcSize >> 7)+4) return 0; /* heuristic : probably not compressible enough */ } DEBUGLOG(6, "histogram detail completed (%zu symbols)", showU32(table->count, maxSymbolValue+1)); /* Check validity of previous table */ if ( repeat && *repeat == HUF_repeat_check && !HUF_validateCTable(oldHufTable, table->count, maxSymbolValue)) { *repeat = HUF_repeat_none; } /* Heuristic : use existing table for small inputs */ if ((flags & HUF_flags_preferRepeat) && repeat && *repeat != HUF_repeat_none) { return HUF_compressCTable_internal(ostart, op, oend, src, srcSize, nbStreams, oldHufTable, flags); } /* Build Huffman Tree */ huffLog = HUF_optimalTableLog(huffLog, srcSize, maxSymbolValue, &table->wksps, sizeof(table->wksps), table->CTable, table->count, flags); { size_t const maxBits = HUF_buildCTable_wksp(table->CTable, table->count, maxSymbolValue, huffLog, &table->wksps.buildCTable_wksp, sizeof(table->wksps.buildCTable_wksp)); CHECK_F(maxBits); huffLog = (U32)maxBits; DEBUGLOG(6, "bit distribution completed (%zu symbols)", showCTableBits(table->CTable + 1, maxSymbolValue+1)); } /* Write table description header */ { CHECK_V_F(hSize, HUF_writeCTable_wksp(op, dstSize, table->CTable, maxSymbolValue, huffLog, &table->wksps.writeCTable_wksp, sizeof(table->wksps.writeCTable_wksp)) ); /* Check if using previous huffman table is beneficial */ if (repeat && *repeat != HUF_repeat_none) { size_t const oldSize = HUF_estimateCompressedSize(oldHufTable, table->count, maxSymbolValue); size_t const newSize = HUF_estimateCompressedSize(table->CTable, table->count, maxSymbolValue); if (oldSize <= hSize + newSize || hSize + 12 >= srcSize) { return HUF_compressCTable_internal(ostart, op, oend, src, srcSize, nbStreams, oldHufTable, flags); } } /* Use the new huffman table */ if (hSize + 12ul >= srcSize) { return 0; } op += hSize; if (repeat) { *repeat = HUF_repeat_none; } if (oldHufTable) ZSTD_memcpy(oldHufTable, table->CTable, sizeof(table->CTable)); /* Save new table */ } return HUF_compressCTable_internal(ostart, op, oend, src, srcSize, nbStreams, table->CTable, flags); } size_t HUF_compress1X_repeat (void* dst, size_t dstSize, const void* src, size_t srcSize, unsigned maxSymbolValue, unsigned huffLog, void* workSpace, size_t wkspSize, HUF_CElt* hufTable, HUF_repeat* repeat, int flags) { DEBUGLOG(5, "HUF_compress1X_repeat (srcSize = %zu)", srcSize); return HUF_compress_internal(dst, dstSize, src, srcSize, maxSymbolValue, huffLog, HUF_singleStream, workSpace, wkspSize, hufTable, repeat, flags); } /* HUF_compress4X_repeat(): * compress input using 4 streams. * consider skipping quickly * reuse an existing huffman compression table */ size_t HUF_compress4X_repeat (void* dst, size_t dstSize, const void* src, size_t srcSize, unsigned maxSymbolValue, unsigned huffLog, void* workSpace, size_t wkspSize, HUF_CElt* hufTable, HUF_repeat* repeat, int flags) { DEBUGLOG(5, "HUF_compress4X_repeat (srcSize = %zu)", srcSize); return HUF_compress_internal(dst, dstSize, src, srcSize, maxSymbolValue, huffLog, HUF_fourStreams, workSpace, wkspSize, hufTable, repeat, flags); }